keith



Nov. 17, 1936.

G. KEITH GAS-FIRED BAKING OVEN Filed Nov. 19, 1935 3 Sheets-Sheet 1 Nov. 17, 1936. KEITH 2,060,993

GAS-FIRED BAKING OVEN Filed Nov. 19, 1935 3 Sheets-Sheet 2 Nov. 17, 1936. G. KEITH GAS-FIRED BAKING OVEN 3 Sheets-Sheet 3 Filed Nov. 19, 1935 Patented Nov. 17, 1936 hiss-mannerisms OVEN George Keitht London England, -r.assignor=. to. Jaricies Keith & Blackman Company Limited; London, England, a company of Great Britain Application November. '19, 1935,. Serial. Nor 50,493

InGreat Britain November 1, 1934 3 Claims; (01. 158-4) Thisainventionarelates to-improvements in gas; fired gloaking ovensxsofarthe rztype equipped with burners. associated with: injectors supplied with gaswunder .pressure,-and has-for an object-to,

,,pro. vide an equipment which-ensures exclusion of dust, which prevents .the reflux flow of vapour fromzthe ovemthroughburners which may be temporarily shut oif and. thereby guards against condensatiomon; and corrosion of, the cool outer parts, and which compensates for tendency to enrichment-got the mixture: when .the gas supply is diminished-.Further. objects are to obviate excessi-ve 1OSSr,Of. :heat at-the' firing. side of theoven,;. and waste of :fan power in overcoming resistance 1 lsejiniair piping:

ASlSillIldGISIlOOd, the standard type of. biscuit cit-bread 1; ovenwcomprises a baking chamber bounded by an -inner-wall. and an outer wall betweenv whichand the innerzwall. lagging is inter:

lposed. .Apertures in-theztwo-.walls-are connected hyopen-endeddistanceiboxes, through which the burners. lead to the -:baleing= .-chamber.i The=injector bcdiesuof.these burners-are usually fixed v exteriorly .ofwtheiouter wall, iandeare. fed with gas Aniovenaccordi-ng to the :present invention is equipped with. wburners incorporating; injectors contrived tow-drawncombustion supporting air at- 30 ,.super-atmospheric pressure from an air space traversedby tuhular.=boxes opening into the interior of the oven, whereby to prevent entry into the burner of dust from the atmosphere or of vapour or products from the oven chamber.

35 The air space is conveniently formed between an outer wall of the oven and a third wall spaced therefrom, being fed by a fan (or fans), so that there is maintained in said air space an air pressure slightly above atmospheric pressure, say

40 from 6 to of an inch water gauge, constituting only a small portion of the pressure of the mixture set up by the injectors.

The invention is illustrated in the accompanying drawings in which Fig. 1 is a vertical section 45 and Fig. 2 a horizontal section showing a burner and the associated parts of an oven. Fig. 3 is a vertical section at right angles to Fig. 1 and Fig. 4 is an elevation at right angles to Fig. 1. Fig. 5 is a fragmentary side elevation and Fig. 6 a

50 transverse section of a biscuit oven embodying the invention. Figs. 7-10 are fragmentary detail views of a burner tube.

Referring to the drawings, I denotes an inner or baking chamber wall, and 2 denotes the usual outer wall of a baking oven, the walls I, 2 defining between thema space 3 .filled with thermal insulating material. 4 denotes a tubular distance box interposed betweensthe "walls :I,'2 so as to interconnect aligned apertures '5, 6 in the walls I, 2,;respectively. Aligned with the distance box l is a second tubular. distance box 'I interposed between the wall 2 and a third Wall 8 defining with the wall'2 an air space 9 which serves as a trunk for supply of combustion-supporting air to the burners for heatingzthe oven, the air pressurewithin the space 9 being maintained slightly:

above atmospheric. pressure. The box I connectsnthewaperture fi'with an aperture II) in a heating plate II abutting on the wall 8 and con stituting, in effect partof the wall 8." The box 1 isiorined near its outer end with a machined cylindricalboreIZ for receptionof a hollow cylindrical plug I3 forming parvofthe body of an injector serving a burner tube I4 carried by the plug I3 and extending through the boxes I, I 4 into the interior of the baking chamber. Ports M in the. wallofzthe box! connect with ports E5 in the plug I3 to admitcombustion-supporting air-from theair space 9 into the interior I6 of theplug I3,:wherein is provided a removable injector nozzle I'I'which discharges a combustible mixtureof gasand inducedair into the burner tube hl througha've'nturi tube I8 accommodated within the end of the burner tube -I4. Gas is taken by way of a pipe-I9 from a header or manifold pipe 2ii' acc0mmodated-in the air space 9 to a pocket 2| presented by the box i, whence it passes to the nozzle I! by way of a manually operable cock 22 located externally of the wall 8 and connecting the pocket 2| with an inlet chamber 23 formed in the plug casting I3 and disposed exteriorly of the wall 8. The cook 22 presents an inlet branch 24 screw-threaded into the pocket 2 i, and an outlet branch 25 coupled to the chamber 23 by a readily disconnectible union 26. The nozzle I! is removable for inspection or replacement through an aperture which opens into the chamber 23 and which is normally closed by a removable screw-threaded plug 21. Regulation of the quality of the combustible mixture delivered into the burner tube I4 is effected by adjustment of a by-pass valve 28 controlling a bypass 29 connecting the chamber 23 with the chamber I6 and opening into the chamber It by way of an annular space 30 surrounding the nozzle I'I.

Combustion-supporting air at super-atmospheric pressure is supplied to an air space 9 common to a plurality of burners, as shown in Figs.

5 and 6,- by a power-driven fan 3| surmounting the oven structure.

The fit of the plug l3 within the bore I2 of the box I may be such that a continuous slight leakage of air takes place to the atmosphere and to the interior of the baking chamber past the inter-engaging surfaces of the bore l2 and the plug IS.

The floating 'plate H overlaps and closes an aperture 32 in the wall 8 and carries externally of the space 9 an annular sealing channel 33 which overlaps the junction of the plate II with the wall 8, The burner may be viewed and lit through a sight-hole 34 closednormally by a door 35 pivoted to the plate II and slidable between the inner face of the plate II and a spring-pressed sealingferrule 36 slidable in a hole 31 in the box I.

To permit withdrawal of the burner unit from the oven, for inspection or repair, it is necessary only to 'uncouple the union 26 so as to disconnect the injector body from the cock 22, after which the burner unit may be withdrawn bodily.

The nozzles 38 are held in non-threaded holes 39 in the tube 14 by a channelled strip 40 pinned to the tube l4 and formed with transverse slots 4| which register with and slightly overlap the nozzles 38, end parts 42 of the slots 4| extending beyond the peripheries of the nozzles to form outlets from the channel space 43 defined between the tube l4 and the strip 40. Combustible mixture is supplied to the space 43 from the tube l4 through small passages 44. As will be understood, the arrangement is such that a flame applied to the nearest of the nozzles 38 will travel along the burner tube and light up the other nozzles 38, the mixture within the space 43 acting, in effect, as a fuse.

I claim:

1. In a gas-fired baking oven having an inner wall and an outer wall, an open-ended distance box interposed between said walls, a third wall forming with said outer wall an air space, an open-ended distance box interposed between said third wall and said outer wall, said second mentioned distance box aligned with said first mentioned distance box, a tubular gas burner extending through said distance boxes into the interior of the oven, an injector for supplying a mixture of gas and air to said burner, said injector comprising a body part within said second mentioned distance box and means for supplying air to said air space and for maintaining super-atmospheric pressure in said air space, said body part and said second mentioned distance box being provided with registering apertures forming the sole passage for air at superatmospheric pressure from said air space to said body part.

' 2. In a baking oven, a wall exterior of said even, a distance box, open at each end, interposed between and spacing said wall from the oven, a fuel burner extending through said distance box into the interior of the oven, said burner including a body part mounted in said distance box,- said body part having an interior fuel-and-air-mixing space, a fuel injector for introducing fuel into said interior space, said distance box and said body part having aligned openings forming passages from the space between said exterior wall and said oven to the interior space of said body member, said passages forming the sole means for passing combustion air to said burner, and means for maintaining a super-atmospheric pressure in the space be tween said exterior wall and said oven, whereby air therein will be caused to flow through said space into the interior space of the body memher to mix with fuel therein.

3. In a baking oven, a wall exterior of said oven, 9. distance box, open'at each end, interposed between and spacing said wall from the oven, a fuel burner extending through said distance box into the interior of the oven, said burner including a body part having a portion of its periphery conforming to the shape of the interior of said distance box and cooperating therewith to close the passage through the same against free passage of air, said body part having an interior fuel-and-air-mixing space, means for introducing fuel into said interior space, said distance box and said body part having aligned openings forming a passage from the space between said exterior wall and said oven to the interior space of said body member, and means for maintaining a super-atmospheric pressure in the space between said exterior wall and said oven whereby air therein will be caused to flow through said passage into the interior space of the body member to mix with fuel therein.

GEORGE KEITH. 

